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Haematology > Haemostasis > Flashcards

Haemostasis Flashcards

1
Q

Which substances are involved in clotting?

A

Platelets
vWF
Coagulation factors

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2
Q

Which substances help to keep the clot confined to the site of injury?

A

Natural anticoagulants

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3
Q

Which system removes the clot?

A

Fibrinolytic system

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4
Q

In normal blood flow, does anything stick to the walls of vessels?

A

No

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5
Q

How are platelets and coagulation factors activated?

A

Receive signals due to:
Abnormal surface
Physiological activator

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6
Q

What is the role of platelets in haemostasis?

A

Adhere
Activation
Aggregation
Provide phospholipid surface for coagulation

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7
Q

What is primary haemostasis?

A

Formation of a platelet plug

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8
Q

What is secondary haemostasis?

A

Formation of a fibrin mesh

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9
Q

What are the steps involved in primary haemostasis?

A

Vasoconstriction

Platelet adhesion

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10
Q

Which substances normally block platelets from sticking to endothelium?

A

Nitric oxide

Prostacyclin

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11
Q

What are nitric oxide and prostacyclin?

A

Vasodilators

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12
Q

What is endothelin?

A

A vasoconstrictor

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13
Q

What are the receptors on platelets involved in haemostasis?

A

Glycoprotein Ib

Glycoprotein IIbIIIa

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14
Q

What is the molecule that provides a link between the site of injury and platelets?

A

von Willebrand factor

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15
Q

Where is vWF normally found?

A

Circulates in blood but is also secreted at the site of injury

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16
Q

What does vWF bind to at the site of injury?

A

Subendothelial collagen on one side and GpIb at the other

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17
Q

What happens when the vWF binds to GpIb?

A

Changes shape of IIbIIIa so that it is now able to bind

Degranulation

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18
Q

What is released by activated platelets into the blood?

A

Granules - alpha granule and dense granule

Thromboxane A2

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19
Q

What does the alpha granule contain?

A

Fibrinogen

vWF

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20
Q

What does the dense garnule (sac) contain?

A

Serotonin
ADP
Ca2+

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21
Q

What is the function of serotonin released by platelets?

A

Smooth muscle constriction

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22
Q

What happens to the ratio of NO/PC to endothelin at the site of injury?

A

NO/PC decreases so endothelin results in vasoconstriction

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23
Q

What is the function of ADP released by platelets?

A

Activates more platelets

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24
Q

What is the function of Ca released by platelets?

A

Required for secondary haemostasis

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25
Q

What is the function of thromboxane A2 released by platelets?

A

Vasoconstriction

Activation and aggregation of platelets

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26
Q

What mediates platelet aggregation?

A

Gp IIbIIIa

27
Q

Why is a fibrin mesh necessary?

A

Links up and aggregates on top of platelet plug to stabilise it

28
Q

What does fibrin circulate as?

A

Fibrinogen

29
Q

What are the ways in which the coagulation cascade can be triggered?

A

Intrinsic pathway - when subendothelial collagen is exposed to the blood
Extrinsic pathway - protein secreted by endothelial cells whenever we have damage to the blood vessels from outside our bodies

30
Q

What is the protein secreted by endothelial cells whenever we have damage to the blood vessels from outside our bodies?

A

Tissue factor/thromboplastin

31
Q

What converts fibrinogen to fibrin?

A

Thrombin

32
Q

What is the inactive form of thrombin?

A

Prothrombin

33
Q

How does the coagulation cascade work?

A

Activated form of each factor activates the next

34
Q

Which factors are involved in the intrinsic pathway?

A

XII XI IX(+VIII) X(+V)

35
Q

Which factors are involved in the extrinsic pathway?

A

III(TF) VII

36
Q

Which factors are activated by thrombin?

A

5, 7, 9, 13

37
Q

What turns plasminogen to plasmin?

A

Thrombin

38
Q

What is the function of plasmin?

A

Acts of fibrin mesh to break them apart

39
Q

What stimulates anti-thrombin to decrease the production of thrombin from prothrombin and conversion of activated factor X to deactivated factor X

A

Thrombin

40
Q

Anticoagulation

A

Prevents clotting

41
Q

Thrombolysis

A

Breaks down clots

42
Q

What is factor V Leiden?

A

Factor V mutation

Makes factor V resistant to protein C

43
Q

What is protein S?

A

Protein C cofactor - helps protein C to work better

44
Q

What is the heparin-like molecule on the surface of endothelium?

A

Anti-thrombin III cogfactor

45
Q

What is the action of anti-thrombin (plus heparin-like cofactor)?

A

Interact to inactivate thrombin and factor X

46
Q

What is the function of a thrombomodulin/thrombin complex?

A

Activation of protein C

47
Q

What are the vitamin K dependent factors?

A

II
VII
IX
X

48
Q

What is the function of vitamin K for certain factors?

A

Adds carboxyl groups whichc is important for enzyme activity

49
Q

What are the fat soluble vitamins?

A

A, D, E, K

50
Q

How are the vitamin K dependent factors measured?

A

PT/APTT/INR

51
Q

Where are factors made?

A

In the liver

52
Q

How does warfarin work?

A

Works on vitamin K dependent factors

53
Q

How do DOACs work?

A

Inhibit thrombin etc

54
Q

What prolongs PT?

A

Decreased level of vitamin K dependent factors
Liver disease (especially cholestasis)
Warfarin
Rarely inherited deficiencies in factors 2, 7, 9 or 10

DIC/DOACs (but APTT will also be prolonged)

55
Q

How does liver disease affect vitamin K dependent factors?

A

Produced in the liver

Fat soluble so bile production has an effect

56
Q

What is cholestasis?

A

A decrease in bile flow due to impaired secretion by hepatocytes or to obstruction of bile flow through intra-or extrahepatic bile ducts, therefore any condition in which substances normally excreted into bile are retained

57
Q

What prolongs APTT?

A 
Haemophilia A/B
vWD (decrease in factor VIII)
Unfractionated heparin (not LMWH)
DIC
DOACs
58
Q

APTT

A

Activated partial prothrombin time

59
Q

What is the cofactor for factor VIII?

A

von Willebrand factor

60
Q

What is used to measure patients on warfarin?

A

INR

61
Q

What aere the causes of DIC?

A

Coagulation is strongly triggered so factors are used up more quickly
Any condition with increased production of TF

62
Q

Which tissues contain a lot of TF and what associated conditions result in DIC?

A 
Brain - brain trauma
Bones - multiple fractures
Placenta - obstetric emergency
Infection - monocytes express TF
Cancer cells express TF (more chronic)
63
Q

How are vitamin K dependent factors activated?

A

Carboxylated by vitamin K

64
Q

Which factors are inhibited by heparin?

A

2, 7, 9, 10

Haematology (18 decks)

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